The central data bank of the Rochester Program Project (RPP) consists of a file of medical diagnoses and surgical procedures covering the population of Rochester and Olmsted County, MN for a period of more than 40 years. These data have been assembled from records at Mayo Clinic and other medical care centers and are considered a national resource for epidemiological studies. The medical records upon which this resource depends cover essentially all local physician-patient contacts and include records for home, outpatient and hospital visits, and autopsy data. This resource is maintained at the Mayo Clinic, but is available to visiting scientists, students from other universities, and health agencies. More than 115 epidemiological studies using this data bank have been completed. These include studies of incidence and outcome as well as case control comparisons and prospective studies. Underway at the present time are several descriptive epidemiologic studies on diabetes, stroke, ischemic heart disease, head trauma, rheumatoid arthritis, fractures of the extremities, pituitary adenomas and various malignant neoplasms; case control studies have been developed on leukemia, ovarian cancer and breast cancer; prospective-type studies are underway on the long term effects of Flagyl and DES; and cost-effectiveness studies have been developed on the CAT (brain) scan, the total body scanner, and manpower needs are being measured for the surgical subspecialties. The BCFF is to be discontinued unless support is forthcoming from another source. In that event, the program will be extended to study many other topics, such as mental retardation, childhood schizophrenia, and other psychiatric and behavioral problems.